Black Death May Have Been Caused by Volcanic Eruption, Study Finds

A climate catastrophe that forced a reconsideration of trade routes was likely responsible for the Black Death in 14th-century Europe, researchers suggest.

Published in the journal Communications Earth & Environment, the new study combines historical documents with analyzes of polar ice cores and European tree rings. Researchers Martin Bauch of the Leibniz Institute in Germany and Ulf Büntgen of the University of Cambridge in the United Kingdom concluded that an unidentified volcanic eruption around 1345 released ash and sulfur into the Earth’s atmosphere, cooling the climate and causing crop failures across the Mediterranean.

This forced the powerful port cities to open trade with the nomadic empire of the Golden Horde Khanate, which dominated Central Asia at the time. In doing so, they ensured safe passage to Europe from Yersinia pestisthe bacteria responsible for the plague.

Italian city-states have successfully developed food security strategies. But they were no match for the plague.

“Through a combination of several coincidences, you get an unexpected side effect. From the perspective of the 14th century, you couldn’t calculate and predict that this would happen: the same system that saves you from starvation will lead to mass death when the Black Death hits your city,” said Bauch, an environmental historian.

Origins of the Black Death

The plague is caused by bacteria Yersinia pestis. The Black Death is the name given to a large wave of plague which ravaged Europe between 1347 and 1351.

If bitten by an animal, such as a flea or rodent infected with the bacteria, the person develops symptoms such as swollen lymph nodes – called “buboes” – and possibly a combination of fever, fatigue, vomiting, nausea and pain. If the lungs become infected, the plague turns into pneumonic plague, a type that spreads more quickly and is always fatal.

Fortunately, the development of antibiotics that kill bacteria has all but relegated the disease to the past. But this problem persists in some parts of the world, including Madagascar, the Democratic Republic of Congo and Peru. Cases have recently been reported in the western United States, Bolivia, and South and Central Asia.

Brazil has not recorded a single human case of plague since 2005, according to the Health Ministry. The last one happened in Ceará. Currently, two areas are considered natural centers of the bacteria: the Northeast region (except Maranhão and Sergipe) and the city of Teresópolis, in the state of Rio de Janeiro.

According to the Ministry of Health, there are other pestigenic areas in the territory of Minas Gerais, in Vale do Rio Doce and Vale do Jequitinhonha, which can be considered an extension of the northeast focus.

The Black Death probably originated in Central Asia. In 2022, another group of researchers from Germany and the United Kingdom managed to identify the origin of the “original strain” of Yersinia pestislinking it to epidemics of 1338 in the Tian Shan mountains, which border present-day Kyrgyzstan.

It is likely that, through trade and human movement, disease-carrying rodents and insects were transported long distances to Western Eurasia and Europe, carrying the plague with them.

Environmental markers, historical implications, trade

How the plague reached Europe has been widely debated by researchers. In this recent study, Bauch and Büntgen used a combination of scientific data and historical documents to detail at least one possible route of disease entry to the continent.

In their paper, they argue that tree rings in eight regions of Europe and volcanic sulfur in polar ice cores show that a large tropical volcanic eruption in 1345 may have caused a climate cooling effect that impacted Mediterranean crops and triggered famine in southern Europe.

Records show that important Italian port cities such as Venice and Genoa negotiated with the Mongolian Golden Horde near the end of this famine to import grain via the Black Sea trade routes.

The region’s supply of grain helped prevent famine among the local population, but probably introduced the plague, which continued to spread across the Italian states as grain reached other cities.

Using environmental references, such as tree rings and ice cores, allows scientists and historians to work together to understand how environmental changes may have influenced social and public health events.

Studies of subtle changes in tree rings and other “natural indicators” contribute to what is called paleoclimate reconstruction – the understanding of ancient climates.

“Only tree rings have the quality that really allows us to connect information,” Bauch said.

Once scientific data is combined with historical records, researchers like Bauch and Büntgen can begin to explain the factors that may have caused major events, including the Black Death.

Maria Spyrou, a paleopathologist at the University of Tübingen in Germany who led the group that identified the origin of the plague in 2022, says Bauch and Büntgen’s new study has added another piece to the puzzle of how the plague infiltrated and infected medieval Europe.

“The study (by Bauch and Büntgen) provides additional evidence that the pandemic emerged in the mid-14th century and is consistent with genetic data showing that the ancestors of the Black Death strains in Europe existed in both the Volga region and the Tian Shan region,” Spyrou told DW in an email.

But Spyrou believes that while the study helps point to another possible route for the plague, it is still not clear how it spread across Central Asia.

Bauch agrees with this assessment. He said their study offers only one of several possible explanations for how the plague entered and spread across Europe in the 14th century.

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